New data on drug and device company payments to doctors largely excludes nurse practitioners and physician assistants, though they play an ever-larger role in health care. One advanced-practice nurse pleaded guilty last month to taking drug company kickbacks.

Medicare has increased oversight of its prescription drug program but many holes remain, allowing fraud and abuse to proliferate. Questionable practices were found at 1,400 pharmacies, which collectively billed Medicare $2.3 billion in 2014.

The move follows an investigation showing that Medicare did little to find dangerous prescribing by doctors to seniors and the disabled. It is also part of the government’s new push to bring transparency to taxpayer-supported medical care.

A new report finds that more than half of insurance companies in Medicare’s drug program haven’t reported fraud cases to the government. The findings echo an earlier investigation that found fraud flourishing in the program.